I. Field of the Invention
The present invention relates generally to valves and more particularly to a manually actuated valve having a hydraulic shut-off mechanism which is responsive to an external hydraulic pressure.
II. Description of the Prior Art
There are many previously known valves. One type of valve comprises a manually actuated valve member having an automatic, high pressure shut-off mechanism so that when the pressure in the lines exceeds a predetermined value, fluid communication in the lines is obstructed.
The disadvantage of the previously known valves with automatic high pressure shut-off mechanisms is that it is often desirable to activate the shut-off mechanism in response to an external pressure rather than the line pressure. Heretofore the previously known valves with automatic shut-off mechanisms responsive to an external pressure have been not only expensive to manufacture but also prone to failure during operation.